sfDomPDFPlugin allows you to convert HTML into a PDF. It is using dompdf library (http://www.digitaljunkies.ca/dompdf/).
This is great for converting things like invoices and customized documents into non-editable PDF format.
Please note, that DomPDF does support CSS 2.1, however it is very picky with the formatting.
Please avoid using shorthand CSS styles or combining styles. For more detail information about styling limitations see the dompdf homepage.